Ubuntu Server: How to change to the root user

  Some guides tell you to enter “su” on Unix systems to get superuser permissions; in Ubuntu, however, this won’t work. As a user with sudo permissions (the user created on install has these) enter the following instead:  
sudo su
  Enter your account password and voila, you are logged in as root. You can tell when you are logged in as root as your prompt will look like:  
[email protected]:/home/#
  rather than:  
[email protected]:/home$  
  Note the # rather than the $? This indicates that you’re performing actions as the root user. This can be dangerous as you will be able to do things which can wreck your system irreparably, so be careful! To go back to working as your usual user, type:  
exit
  or hit CTRL+D.